"Not having enough memory restricts the number of virtual machines, and also restricts the overall performance. Not having enough memory is either down to improper planning, or in most cases, the inability to purchase enough memory due to the higher cost of OEM memory," it said.

In the US the Magnuson Moss Act restricts vendors from scaring customers into purchasing expensive OEM memory, the company said. "However, in the UK such constraints do not yet exist, and therefore there is a need to educate customers that they can use (third-party) memory without voiding their warranty."

Rhys Austin, who runs the virtualisation practice for industry standard servers at HP agreed that too little memory will affect virtualisation performance but strongly rejected Kingston's assertion that users were worried about price or warranties.

Austin said that while there may be "instances in time" where HP memory is over 20 percent more expensive than other memory products, HP's server market share indicated that users did not feel overcharged for their memory products.

"Adding third-party warranty in no way violates the warranty on that server. Naturally HP can't warranty third party memory and we work hard to ensure that the configuration of the memory we supply is correct. We have never underspecified system memory to sell a server," said Austin.